Poly(hydroxyarylpolymethylenesulfonium)zwitterionic monomers and surface coatings therefrom

ABSTRACT

POLY-(HYDROXYARLYPOLYMETHYLENESULFONIUM) SALTS OF FORMULA I:   (((-CH2-A-(B)C-CH2-)&gt;S(+)-),R,(R&#39;&#39;)A,HO-PHENYL)-(Z-((R&#39;&#39;)A,   HO-PHENYLENE))X-(Z-((R&#39;&#39;)A,((-CH2-A-(B)C-CH2-)&gt;S(+)-),HO-   PHENYLENE))Y-R (X(-))2   WHERE Z IS -CH2- AND $(X+Y)-1-20, ARE PREPARED BY CONDENSATION OF A POLYNUCLEAR PHENOL WITH A CYCLIC SULFIDE. THESE SALTS CAN BE CONVERTED INTO A CYCLIC SULFONIUM HYDROXIDE INNER SALT OR ZWITTERIONIC MONOMER (II). THESE REACTIVE CYCLIC SULFONIUM ZWITTERION MONOMERS THERMALLY POLYMERIZE TO YIELD WATER-INSOLUBLE, THERMOSET RESINS USEFUL AS ADHESIVES, COATINGS, FILMS, AND IMPREGNANTS. APPLIED TO NONPOROUS SURFACES, SUCH AS GLASS AND WIRE, HARD SURFACE COATINGS WITH HIGH IMPACT RESISTANCE COUPLED WITH GOOD WATER AND CHEMICAL RESISTANCE ARE OBTAINED.

United States Patent POLY(HYDROXYARYLPOLYMETHYLENESULFO- NIUM)ZWITTERIONIC MONOMERS AND SUR- FACE COATINGS THEREFROM Melvin J. Hatch,Socorro, N. Mex., and Donald L. Schmidt and Hugh B. Smith, Midland,Mich, assignors to The Dow Chemical Company, Midland, Mich.

No Drawing. Continuation-impart of application Ser. No. 866,762, Oct.15, 1969. This application Dec. 7, I971, Ser. No. 205,755

Int. Cl. C07d 63/04, 65/04 US. Cl. 260332.3 R 10 Claims ABSTRACT OF THEDISCLOSURE Poly(hydroxyarylpolymethylenesulfonium) salts of Forwhere Zis -CH and E(x+y)=l-20, are prepared by condensation of a polynuclearphenol with a cyclic sulfide. These salts can be converted into a cyclicsulfonium hydroxide inner salt or zwitterionic monomer (II). Thesereactive cyclic sulfonium zwitterion monomers thermally polymerize toyield water-insoluble, thermoset resins useful as adhesives, coatings,films, and impregnants. Applied to nonporous surfaces, such as glass andwire, hard surface coatings with high impact resistance coupled withgood Water and chemical resistance are obtained.

BACKGROUND This application is a continuation-in-part of US. applicationS.N. 866,762, filed Oct. 15, 1969, now US. Pat. No. 3,660,431.

The thermal lability of many sulfonium salts is recognized. HatchCanadian Pat. 708,230 and British Pat. 960,029 describe film-formingcompositions containing a sulfonium binder which on heating forms awater-insoluble film. Lloyd US. Pat. 3,409,660 and Kangas US. Pat.3,322,737 use sulfonium salts as fugitive surfactants and stabilizers inthermally curing latex systems.

In the thermal polymerization of certain sulfonium carboxylate saltsdisclosed by Hatch, the condensation of the monomeric salt containing anequal number of positive and negative sites yields a polyester andby-product sulfide such as the classical nylon salt polymerizationyields a polyamide and water. As in the nylon polymerization, by-productsulfide normally requires special processing for complete removal fromthe product.

STATEMENT OF THE INVENTION A new class of poly(hydroxyaryl cyclicsulfonium) salts has been discovered which form reactive inner hydroxidesalts or zwitterions. These cyclic sulfonium zwitterions, containing anequal number of positive and negative charge sites, are very reactivemonomers. They thermally polymerize without sulfide by-products, thesulfur and attached organic groups becoming part of the polymerstructure. With an average of more than one cyclic sulfonium zwitterionper monomer unit (men), crosslinked polymer resins are obtained.

fit

More specifically, new poly(hydroxyarylpolymethylene sulfonium) saltshaving Formula I have been prepared and used to synthesizepoly(hydroxyarylpolymethylene sulfonium)zwitterionic monomers havingFormula II, i.e.:

M It J each R individually is H, Cl, Br, OH, or OC C alkyl,

each R individually is H, Cl, Br, or C -C alkyl and a is 1 or 2;

each sulfur is ortho or para to a phenolic oxygen,

each A and B individually are -CH or -CHR' and c is 1 or 2, and

X is a nonbasic inorganic anion; and

Preferably X is the anion of a strong inorganic acid such as Cl-, Br-,H50 and HClO The zwitterionic monomers (II) thermally polymerize toyield solid polymers containing as an essential element a plurality ofoxyarylthioalkylene groups having Formula 111:

GENERAL DESCRIPTION Poly(hydroxyaryl cyclic sulfonium) salts (I) Thesepoly(hydroxyaryl cyclic sulfonium) salts are prepared from polynuclearphenols such as bisphenol, di (hydroxyphenyDether,di(hydroxyphenyl)sulfide, bis(ohydroxyphenyl) C -C alkylene glycolether, and phenol formaldehyde resins by processes such as follows:

where P is the remaining portion of the phenolic monomer.

These processes require that the phenol reactant have at least oneactive ortho or para hydrogen per intended sulfonium group. Strongelectron-withdrawing substituent groups, such as halogen, carboxylateand nitro, deactivate the polyphenol and cause poor yields. Thus, thehaloaryl sulfonium salts are preferably prepared by direct halogenationof the sulfonium salt.

Hydroxyaryl sulfonium salts having an average of 1 or less sulfoniumgroups per molecule normally yield soluble, essentially linear polymer.With an average of more than 1 sulfonium group per molecule,cross-linking and insolubilization occur during the subsequentpolymerization.

Process IA is carried out in the dark at a reduced temperature, such as-40 to -l0 C., and gives moderate yields of the polyphenolic cyclicsulfonium chloride. At lower temperatures, yields are improved by addinganhydrous HCl to the tetramethylenesulfide prior to adding thepolyphenol and C1 In process IB, a polynuclear phenol andtetramethylenesulfoxide condense in the presence of a strong anhydrousacid such as HCl. Methanol can be used as a solvent. Low temperaturesand a Lewis acid catalyst such as AlCl S0 etc., are useful in minimizingside reactions and improving color.

By appropriate choice of reactants, process, and process conditions, awide variety of poly(hydroxyaryl cyclic sulfonoum) salts can beprepared.

Typical polynuclear phenol reactants include bisphenols, such asmethylenebis(phenol) and isopropylidenebis (phenol),di(hydroxyphenyl)ether, di(hydroxyphenyl) sulfide, bis ethers and estersof catechol and resorcinol with C -C alkylene glycols and C -Cdicarboxylic acids. Useful sulfides and sulfoxides includetetramethylenesulfide, tetramethylenesulfoxide, pentamethylenesulfide,and pentamethylenesulfoxide.

The cyclic sulfonium salts with a nonbasic inorganic anion such aschloride or bromide, are generally stable, solid salts at roomtemperature, soluble in polar hydroxylic solvents such as water,methanol and isopropanol. Stable hydrates have been isolated of somesalts. Illustrative of their chemical stability is the chlorination ofthe bissulfonium salt of isopropylidenebisphenol with chlorine to yielda chlorinated sulfonium salt.

Purification of the salts can be achieved by crystallization from amixed solvent such as methylene chloridemethanol, conversion into aninsoluble salt e.g., sulfate or perchloroate, or precipitation fromaqueous solution with a precipitant diluent such as dioxane,tetrahydrofuran, or higher alcohol.

Poly(hydroxyaryl cyclic sulfonium) zwitterionic monomers (II) Conversionof the sulfonium salt (I) into the reactive, sulfonium hydroxide innersalt or zwitterionic monomer (II) is achieved by known methods.Ion-exchange with an anion-exchange resin in hydroxide form isparticularly suitable. For some salts, direct treatment with a stronginorganic base in a solvent such as anhydrous alcohol in which theby-product inorganic salt has limited solubility is preferred.

Isolation of the crystalline zwitterionic monomer from solution iscomplicated by polymerization as the solvent is removed. However, stablecrystalline hydrates have been isolated in some cases. The structuralidentity of the zwitterionic monomers has been confirmed byspectrographic analyses.

For many applications the zwitterionic monomer is advantageously used insolution. Thus, the monomer can be applied to a surface as an aqueoussolution. Evaporation of the solvent yields a partially polymerized filmthat can be cured by further heating to a hard, resilient coating.

Polymerization Thermal polymerization of the poly(hydroxyaryl cyclicsulfonium) zwitterionic monomer (II) is a facile reaction involvingattack of a phenolic anion on a methylene carbon adjacent to thesulfonium group in the cyclic sulfonium ring with cleavage of the ringand formation of a polymer having a plurality of moieties of FormulaIII, e.g.,

where P is the remaining portion of the phenolic monomer. As in othercondensation polymerizations, essentially linear polymers are obtainedfrom zwitterionic monomers containing about 1 sulfonium zwitterion permolecule. With an average of more than 1 sulfonium zwitterion permolecule, cross-linking and insolubilization are obtained duringpolymerization.

Copolymers are prepared from mixtures of sulfonium zwitterionic monomersincluding the zwitterionic monomers derived from mono(hydroxyaryl cyclicsulfonium) salts described by Hatch, Yoshimine, Smith and Schmidt in US.application Ser. No. 866,763 filed Oct. 15, 1969 and now U.S. Pat. No.3,636,052. By appropriate choice of reactants, copolymers can beobtained with varied degrees of cross-linking, thus permittingmodification of the hardness, flexibility, resilience, and otherimportant physical properties of the polymers.

Although some polymerization may occur at room temperature, differentialthermal analysis reveals a major polymerization exotherm for thezwitterionic monomers between about 40100 C. Thus, rapid polymerizationis generally obtained by heating at about 40-200 C. Particularly incoating applications, it is often desirable to achieve partialpolymerization as the solvent is evaporated at 20100 C. and then a finalcure by heating for a short time at a higher temperature, preferablyabout -150 C.

Higher molecular weight polymers are normally obtained by polymerizingin the absence of oxygen. In some instances, addition of a nucleophilicamine initiator increases the polymer molecular weight.

The thermal polymers typically have glass transition temperaturesbetween about 30-110 C. and decomposition temperatures greater than 300C. as determined by difierential thermal analysis. The polymers alsohave good water and solvent resistance.

Films and coatings The thermal polymers of the poly(hydroxyaryl cyclicsulfonium)zwitterionic monomers (II) described herein are particularlyuseful as adhesives, impregnants, coatings and films when the zwitterionmonomer can be applied to the substrate or cast from solution andthereafter dried and polymerized in situ. Such coatings can be appliedto nonporous surfaces, such as glass and metals, in many forms includingsheets, films, wires, filaments, beads, etc., to give strong, durable,protective surface coatings by simple and conventional methods. Porousmaterial, including paper and other cellulosic products, textile goods,wood, etc., can also be impregnated or coated with a solution of thesulfonium zwitterionic monomer by standard techniques followed by insitu thermal curing.

Since the sulfonium zwitterionic monomers are very soluble in water andother polar solvents, e.g., 50-70% by weight, relatively thick coatingsare easy to obtain. When desired, appropriate pigments and other coatingadditives can be incorporated in the monomer solution and then fixed inthe coating during polymerization. Other advantages arise from thestrong adherence of these polymers to the substrate surface and theshort curing times required.

The following examples illustrate further the present invention. Unlessotherwise stated, all parts and percentages are by weight.

EXAMPLE 1 Phenol-formaldehyde novolak tetramethylene sulfoniumzwitterionic monomers (A) To a solution of pts. (0.1 mole) ofbis(2-hydroxyphenyl)methane and 10.4 pts. (0.1 mole) tetrahydrothiopheneoxide at 0-10 C. was added 72 pts. (2.0 moles) of dry HCl over 0.5 hour.The mixture was stirred cold for another 0.75 hour and then slurriedwith acetone-ether. The solid sulfonium chloride was recovered and airdried, yield 16 pts. (75%).

The methylenebis(4-hydroxy-m-phenylene)bis(tetrahydrothiophenium)chloride wasion-exchanged with a resin in hydroxide form to yield a solid whitezwitterionic monomer (IIC). NMR analysis confirmed this structure as ahexahydrate. A sample heated briefly on a hot plate at 150-200 C. gave ahard, cross-linked polymer.

do as (B) A water-soluble phenol-formaldehyde novolak resin having anaverage degree of polymerization (DP) of 4.5 was condensed with 4.5moles tetrahydrothiophene oxide in the presence of HCl as described inExample 1A and then converted into a sulfonium zwitterionic monomerhaving an average of more than 1 sulfonium group per molecule. Yield13%. This monomer partially polymerized at room temperature.

(C) In another run, a water-soluble novolak resin having an average DPof 2.5 was condensed with about 0.33 mole of tetrahydrothiophene oxideper phenolic OH. Analysis of the recovered water-soluble monomer incyclic sulfonium zwitterion form indicated an average degree ofsubstitution of about 1.3. The same novolak resin with a slight excessof tetrahydrothiophene oxide gave a sulfonium monomer containing anaverage of 1.0 8 phenolic OH.

The IR and NMR spectra of these sulfonium salts and zwitterionicmonomers were consistent with structural Formulas I and II, e.g.:

where Z(x+y)=1-4. A detailed study of the NMR spectra of the initialnovolak resins in d -pyridine solution and the cyclic sulfonium monomersin CF COOH with tetramethylsilane as the internal chemical shiftreference established that the water-soluble sulfonium monomers wereobtained from novolak resins having less than about 35 mole percent0,0'-methylene bridging.

Other phenol-aldehyde condensation resins as described in MegsonPhenolic Resin Chemistry Academic Press, New York 1958, can be used asthe polynuclear phenol reactant. Particularly suitable are thephenol-formaldehyde novolak resins prepared by condensing about 0.7- 1.0mole formaldehyde with 1 mole phenol to give a soluble novolak resinhaving a degree of polymerization of up to about 20 as described forexample in British Pat. 615,335. These sulfonium salts and zwitterionicmonomers have structures consistent with Formulas I and II where R, Rand R" are H and 2(x+y) is 1-20, and preferably about 1-4. Halogenatedderivatives can be prepared by chlorination or bromination of the cyclicsulfonium salts.

EXAMPLE 2 Polymerization of the poly(hydroxyaryl)tetramethylenesulfonium zwitterionic monomers The sulfonium zwitterionic monomers ofExample 1 polymerize when heated at about 40'-200 C. Typically theditferential thermal analysis (DTA) curve of a biscatechol trimethyleneether sulfonium monomer showed a polymerization exotherm between about60100 C. The resulting polymer had DTA endotherms at 50 and 350 C.corresponding to the glass transition temperature, T and thedecomposition temperature. In some instances, the zwitterionic monomerscould not be isolated in crystalline form at room temperature because ofpolymerization as the solvent is removed.

Applied as an aqueous or alcoholic solution to a surface and then driedand heated, these poly(hydroxyaryl)- tetramethylene sulfoniumzwitterionic monomers yield water resistant coatings. Cross-linkingoccurs with an average of more than 1 sulfonium zwitterion group permolecule to yield hard coatings. Blended with a chain extending cyclicsulfonium monomers such as the tetramethylene sulfonium monomer fromphenol, o-cresol or 2,6-dichlorophenol, the cross-linking polycyclicsulfonium monomers provide coatings with controlled hardness andflexibility.

TABLE 1.-COATED STEEL PANELS Hard- Impact,

Number Novolak resin ness B in.-lbs.

1 I-l (z=0, 11=2.5) 25 160 2 I-2 (9:=0, 1l=3.5) 39 3... 50% I2+50%o-cresol 18. 7 4 50% I-l, 50% I-2 35 160 Kentron-Knoop Hardness, ASTMmethod D 1474-62T. b AS'IM method D-522-60.

7 We claim: 1. A poly(hydroxyarylpolymethylene sulfonium) salt havingFormula I:

OH R. H R's] OH R5,] 2 z s x sxe where each R individually is H, Cl, Br,OH, or OC -C alkyl,

each -R individually is H, Cl, Br, or C -C alkyl and a is 1 or 2;

each sulfonium group is ortho or para to a phenolic oxygen,

each A and B individually are CH or -CHR'- and c is 1 or 2,

X is an acidic inorganic anion, and

6. A soluble poly(hydroxyarylpolymethylene sulfonium)zwitterionicmonomer having Formula II:

CHg O 1 where each R individually is H, Cl, Br, OH, or OC -C alkyl,

each R individually is H, Cl, Br, or C -C alkyl and a is l or 2;

each sulfonium group is ortho or para to a phenolic oxygen,

each A and B individually are CH or CHR'- and c is 1 or 2,

Z is CH and E(x+y)-=1-20.

7. The cyclic sulfonium zwitterionic monomer of claim 6 where A(B) is CHC H 8. The water-soluble cyclic sulfonium zwitterionic monr omer ofclaim 6 where 2(x+y)-=14.

9. The water-soluble cyclic sulfonium zwitterionic monomer of claim 6having the formula:

10. The water-soluble cyclic sulfonium zwitterionic monomer of claim 9containing less than about 35 mole percent 0,0'-methylene bridging.

References Cited UNITED STATES PATENTS l/1972 Hatch et al. 260332.35/1972 Hatch et al. 260-3322 HENRY R. JILES, Primary Examiner C. M. S.JAISLE, Assistant Examiner U.S. Cl. X.R.

